Aliso Canyon Air Sample Results

Although experts agree that natural gas is not considered to be a toxic or hazardous air pollutant and that the amount of odorant in natural gas is too low to be a health concern, we recently conducted air sampling to provide the community with more information. SoCalGas will continue to conduct air sampling in multiple locations within the community until odors associated with the leak have abated.

The California Office of Environmental Health Hazard Assessment (OEHHA) has completed an assessment of six weeks of air samples taken from areas around the Aliso Canyon storage facility, and their results state that “available Porter Ranch neighborhood air sample data does not indicate that an acute toxicity health hazard exists in the Porter Ranch neighborhood as a result of the Aliso Canyon natural gas leak”. For details from OEHHA, please click here.

Methodology

Our methodology for the collection, handling and analysis of air samples followed the testing procedures approved by the Environmental Protection Agency (EPA) and the South Coast Air Quality Management District (SCAQMD). Samples were collected using SUMMA canisters and Tedlar bags and immediately transported to a laboratory. Using methods prescribed by EPA and SCAQMD, the lab analyzed each of the samples for the presence of natural gas constituents, including odorant.

Our methodology for selecting sampling sites involved a combination of fixed and variable criteria – including wind patterns and customer odor complaints. In addition to collecting air samples at locations within our facility, we also collected samples in several public locations within the community, such as parks, trails, schools and around the area outside our facility. We collected samples at different hours of the day, concentrating on the morning and late-night hours during which most complaints were received.

Summary of Findings (samples taken on October 30 - July 21) as Assessed by Dr. Mary McDaniel**

12-Hour Air Sampling

•12-hour air sampling began Monday January 11, 2016 at 9 locations – 3 within the facility and 6 along the facility boundary closest to the community. Two 12-hour samples were collected each day from each location and the results are posted here.

•Community outdoor air sampling will continue to be performed every twenty-four hours. To date, none of the samples have returned any findings that pose a health risk to the community or to workers at the facility.

Methane, Benzene and Toulene Levels

•The levels of methane detected in outdoor air do not present a health risk. As expected, the highest levels of methane have been detected in samples collected near the leaking storage well. The levels detected in the neighboring communities have been much lower and well within safe limits.

•Results for air samples collected outside the Porter Ranch Community School, Castlebay Elementary, and Starter Set School have shown that methane, benzene, other hydrocarbons and the odorants all have been within safe levels.

•Benzene and toluene have been detected at extremely low concentrations in samples collected around the community, consistent with levels expected for this area. On November 10, two of the eight samples collected within the community were slightly higher (3.5 to 5.5 ppb). In the early morning of November 11, benzene in these areas returned to below 1 ppb.

•As expected, the highest levels of benzene have been detected in samples collected at the storage facility. The maximum detect is well below the 8-hour safe workplace standard of 1 part per million (or 1000 ppb) set by the California Occupational and Safety and Health Administration (Cal OSHA).

Odorant Levels

•Neither of the odorants added to the Aliso Canyon natural gas (t-butyl mercaptan and tetrahydrothiophene) has been detected in air samples collected at the facility or in the community. The reporting limits (level at which a compound can be detected by the laboratory) for these compounds range from approximately 2 ppb to 5 ppb. However, the odorants can be smelled at very low levels (less than 1 ppb), far below levels of health concern and just below the laboratories’ abilities to detect them.

Sulfur Compound Levels

• In addition to the two chemicals in the odorant, other sulfur-containing compounds may be found in natural gas. To date, the sulfur compounds detected in community air samples have been limited to hydrogen sulfide, sulfur dioxide, and carbon disulfide.

•Hydrogen sulfide, sulfur dioxide, and carbon disulfide were not detected in the gas leaking from the well; therefore, it is unlikely that the detections in air of these sulfur compounds related to the gas leak. Further, these compounds have been detected intermittently and at very low concentrations below levels of health concern. However, a single ten-minute sample taken on November 12, 2015 PM from the Porter Ranch Estates location showed levels of hydrogen sulfide (183 ppb) and sulfur dioxide (54 ppb) above the California Ambient Air Quality Standards. These compounds are not known to be associated with the gas leak and the level of methane detected in the sample was very low (methane is the major component of natural gas). Because this was a single sample of limited duration, adverse health impacts are not expected. The air quality agencies were informed of the result and it was posted to the website.

**Dr. Mary McDaniel, a consultant to SoCalGas, is board-certified in occupational and environmental medicine and is the medical director of Intrinsik Environmental Sciences.

***A Note on Air Sample Results

***Due to a processing backlog with external laboratories, we are experiencing a slight delay in posting air sample results. We are working diligently to post air sample results as soon as we receive them.

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